Psychobiotics, immunology, and the theory of all chronic disease.
We are never truly alone. On our skin, in our gums, and in our guts live 100 trillion organisms, altogether known as the microbiome. These beasties comprise 90% of the cells of our bodies, though these cells are so tiny in size that it appears our own human cells predominate. It is only recently that we have begun to study these organisms with any depth. Most of them live within the gut, and cannot be cultured, and only with the advent of advanced genetic testing have we been able to have a better understanding of the variety and numbers of microbes we’re dealing with. They are Bacteria, Archaea, and even some eukariotic parasites, protozoans, and fungi.